A common type of electrical submersible pump comprises a centrifugal pump suspended on a string of tubing within a casing of the well. The pump is driven by a downhole electrical motor, normally a three-phase AC type. A power line extends from a power source at the surface alongside the tubing to the motor to supply power.
Typically the power line is made up of two sections, a motor lead and a power cable. The motor lead has a plug on its lower end that secures to a receptacle known as a “pothead” at the upper end of the electrical motor. The motor lead has three conductors that are insulated and located within a single elastomeric jacket that is extruded around the assembled insulated conductors. Metallic outer armor may wrap around the jacket of the motor lead to avoid damage to the motor lead while running the pump assembly into the well. The motor lead extends upward beyond the pump, for example from 10 to 80 ft. The total of the motor lead and pothead is known as the motor lead extension (MLE). The lead could exceed 80 ft or be shorter than 10 ft depending on the application. A splice connects the motor lead to the power cable. The motor lead is flat and smaller in dimension than the power cable so that it can pass between the pump assembly and the casing.
The power cable comprises three conductors, each having one or more layers of insulation. An elastomeric jacket is usually extruded over the assembled conductors. In some cases, the insulated conductors are encased in lead. The insulated conductors are arranged either in a flat side-by-side configuration, or in a round configuration spaced 120 degrees apart from each other relative to a longitudinal axis of the power cable. A metallic armor is typically wrapped around the jacket to form the exterior of the power cable.
In some wells, the formation temperature is quite hot. Also, the motor generates heat. At least one of the insulation layers of each conductor may be formed of a polymer that is resistant to high temperature degradation. However, current high temperature polymer materials may not be capable of withstanding the high temperatures and harsh environments in some wells. If the insulation degrades, a short could result that would require the pump assembly to be pulled and replaced. Conventional pothead designs that are capable of withstanding these extreme conditions are generally bulkier and have large profiles. However, there are some situations in which the target wells have size limitations that prevent the use of these conventional pothead designs. Therefore, it would be beneficial to have a pothead design that is operable to work in harsh conditions while maintaining a small profile.